People and young people have having less sex and less of everything because of poorer circumstances combined with an inability/reflectance to compromise.
Applied to housing this means that it is economically harder to afford a house so people stay home in their parents mcmansions. It's hard to afford/own a home because people don't want to buy a starter home so no one builds them. Finally it becomes very profitable if you have the cash to flip old houses thus quickly exhausting the supply of cheaper housing.
Speaking of living in places that could be called mcmansions, they are not bad to live in. While you could say a family as a unit is better off with a smaller 70s tri level, the mcmansions has more space so each individual feels like they get what they want. The main rooms remain clean and uncluttered while the messy lives of children are confined to bedrooms. The interior is vast enough to support guests and extended family, etc.
For movies, the consolidation of production means that having many movies is just competing with yourself. Producing a single film for 90% of the demographics is cheaper and makes more money. A decent percentage of America is quite religious and won't take there 3 12 year olds to anything containing sex. Thus most movies now don't contain it. Anything with sex becomes too taboo to view with the family which just reinforces this effect. The current wave of social justice also makes sex an untouchable topic both for movies and in real life.